Phosphine borines and their preparation



United Sttes Patent Ofice 3,117,157 Patented Jan. 7, 1964 ware No Drawing. Filed Mar. 2, 1959, Ser. No. 796,224

6 Claims. (Cl. 260543) This invention relates in general to phosphine borines and more particularly to phosphine borine compounds which may be added to gasoline which may contain tetraethyl lead (TEL) and which will probably contain ethylene dichloride and dibromide (in the case of automotive fuels) and ethylene dibromide alone (in the case of aviation fuels), the phosphine borines serving to reduce preignition of the gasoline when it is used as a motor fuel.

It is an object of this invention to provide for the preparation of certain phosphine borines which are particularly useful as preignition additives for gasoline; that is, the materials to which this invention is directed may serve as additives to reduce preignition of gasoline.

Ancillary objects and advantages of this invention, if not specifically set forth, will become apparent during the course of the description which follows.

Broadly, this invention relates to phosphine borines of the general formula R R"P:BRYX wherein R is a lower alkyl radical, R" is selected from the group consisting of lower alkyl and phenyl radicals, where R represents a lower alkyl radical (one carbon to eight carbons) or a phenyl or alkyl-substituted phenyl radical, where X represents C1 or Br and where Y represents an alkyl radical of from one to eight carbons, C1 or Br. These materials may be added to unleaded gasoline or gasoline which contains TEL or a similar metal-containing antidetonant, as set forth in our co-pending application, Serial No. 796,223, filed March 2, 1959, and serve therein as excellent preignition additives.

When the phosphine borines of this invention are added to motor fuel, the resulting motor fuel is found to have a low preignition index and a high resistance to detonation knocking. Another elfect of the use of these phos phine borines is to decrease the tendency of the presence of TEL in the gasoline to raise the octane requirement of the engine in which the gasoline is used. A further advantage of these phosphine borines as gasoline additives is that such phosphine borines are highly resistant to hydrolysis, as a result of which they have little tend ency to be leached from the fuel by the action of such free water as may be present.

In this respect, the phosphine borines as a class are decidedly advantageous as compared with most other boron-containing gasoline additives which are highly vulnerable to hydrolysis. A further desirable feature of such phosphine borines is that they are liquids or lowmelting solids amply soluble in hydrocarbons. These properties are important in gasoline additives since additives which have high-melting points or low solubilities have strong tendencies to precipitate and form solid deposits when the fuel mixture is vaporized in the carburetor. Such deposits cause malfunctioning of the engine in addition to defeating the purpose of feeding the additive into the combustion chamber. Liquids are also desirable from a material-handling standpoint since they may be blended conveniently with liquid fuels. The phosphine borines of the present invention, while highly soluble in hydrocarbons, are relatively insoluble in water; this tends to maintain quantitative requirements at low levels since there is essentially no loss by extraction.

Finally, the fact that halogen is here introduced in the form of the phosphine borine compound permits a reduction in the amount of ethylene dihalide normally required in leaded gasoline; this enables a reduction in costs by providing means for simultaneously controlling ignition and scavenging lead with a single additive.

Such a phosphine borine, when used as a preignition additive for gasoline, combines the known beneficial effects of both boron and phosphorus in a single molecule of relatively small size and low molecular weight, but,

unexpectedly, small amounts of the phosphine borines are found superior to mixtures of individual commercially-available preignition additives containing phosphorus on the one hand and boron on the other. Further, the phosphine borines are relatively non-reactive and resist decomposition, even at relatively high temperatures.

The quantities of these materials which are most effective in gasoline and details of their effects upon the gasoline will not be further described here, as this information is set out in the afore-mentioned co-pending application.

Examples of preferred compounds falling within the scope of the general formula given above are:

It will be noted that the peculiarity of the various phosphine borines set forth above is that each has mixed substituent types bonded to the boron; that is, each of these phosphine borines has at least a single alkyl group and at least a single chloro or bromo substituent on the boron. This particular configuration, coupled with the fact that three hydrocarbon groups are bonded to the phosphorus, gives these materials particular useful properties as mentioned in the foregoing.

A possible explanation for the unique properties of the compounds herein described, as compared with properties of other phosphine borines, is that the particular properties required for greatest effectiveness and utility as preignition suppressants for motor fuels are maximized in the instant compounds. Alkyl groups on phosphorus increases the strength of the PB coordinate bond by increasing the availability of the donor electrons; hence phosphine borines derived from tertiary phosphines are more stable than those derived from secondary or primary phosphines or the unsubstituted PH stability decreasing in the order named. Alkyl groups on the boron atom, on the other hand, decrease the P-B bond stability as compared with halogen substituents. Halogen substituents on boron increase the Lewis acidity of the borine moiety, thereby strengthening the PB bond with the result that hydrolytic, oxidative, and thermal stability of the phosphine borine is enhanced. Aromatic substituents on boron exert an intermediate effect, as compared with alkyl groups and halogens. While halogen substituents on boron are desirable for these effects as well as for their lead-scavenging action, the halogens, at the same time, tend to decrease the volatility and hydrocarbonsolubility and to increase the melting point of the phosphine borine. Furthermore, since the symmetrical molecules in general have higher melting points than less symmetrical molecules, phosphine borines having BX R and BXR groups have substantially lower melting points than those having BX groups, because of both steric and electronic effects. Thus, an optimum combination of physical and chemical properties is apparently reached in phosphine borines of the type R PzBRYX. It is not 3 desired, however, to limit the invention to any particular theory.

A general preparative method for these new compounds is as follows: To a weighed quantity of a boron compound of the formula BR'YX contained in a suitable reaction vessel is added an equimolar quantity of the tertiary phosphine selected at such a rate that the evolved heat can be dissipated by external means. The reverse procedure may also be used, but it is somewhat less convenient.

A large number of tertiary phosphines are described in the literature. See, for example, pages 31-37 of Organophosphorus Compounds, Kosolapofl, New York, John Wiley & Sons, 1950. The alkyl groups attached to phosphorus may be the same or different. Tertiary phosphines having three identical alkyl groups are preferred because they are much more readily prepared than unsymmetrical tertiary phosphines. The preparation of various of the boron-containing precursors is described at pages 1099-1052 of Organic Compounds of Boron, M. L. Lappert, appearing in the Chem. Rev., 56, 959 (1956). Preparation of various of the boron compounds is also set forth in application Serial No. 707,124, filed January 6, 1958, for Organo-Boron Compounds, and application Serial No. 720,067, filed March 10, 1958, for Preparation of Dihaloborines. Still another disclosure of the preparation of these borines is that in Patent Number 2,940,999.

The preparation of various other possible reactants, compounds of the formula ArBX where Ar is an aryl group, is set forth in co-pending application Serial No. 787,106, filed January 16, 1959, for Preparation of Aryldihaloboranes and Poly(dihaloborano)benzenes.

The specific example set forth below shows the preparation of the materials of this invention, but this is for illustrative purposes only and is not to be interpreted as imposing limitations on the scope of the invention other than as set forth in the appended claims.

Example.Ethyldichloroborine containing a small amount of boron trichloride was fractionally condensed at 78 C. to remove the more volatile impurity. On the high vacuum system 40.0 g. (0.36 mole) C H BCl was condensed at 78 C. in a 500 ml. round bottom flask which was then filled with dry nitrogen and fitted with a 78 C. reflux condenser, addition funnel, and stirrer. The system was flushed with nitrogen vented through a mercury bubbler after which the flask was allowed to warm to room temperature. A 70.9 g. (0.35 mole) quantity of tributylphosphine was added at such a rate that the temperature of the reaction mixture remained liquid at approximately 60 C. On completion of the addition of the tertiary phosphine, the excess C H BCl ceased to reflux and the apparatus was again flushed with nitrogen. The molten adduct was degassed under high vacuum to remove excess reagents. The solid product, (C H P:BCl C H weighing 109 g. (0.348 mole), assayed 92% of the desired material, with (C H P:BCl being the principal contaminant. The product had a melting point of 5458 C. and was soluble in hydrocarbons of the gasoline boiling range (65110 C. petroleum ether) to the extent of about 21.6 g. per liter of solvent.

Following the method set forth above, various other materials may be prepared; see the table below:

Phosphine Boriue Phosphiue-Boriue Product (CHahP. (CH3)3P:BClzCH3 (CH P BBKCHa); (CHa)3P:BBr(CH (C Hg)3P BBIgCgHs. (C4HB)3PIBBI'2G2H5 C5H5(CH3) 3P, 1301203117 C@H5(CH3) 2P 2 1301263117 8 P a 11)s I 2 4 n As aforementioned, a test for preignition has been devised and the new compounds of this invention have been compared with other closely related compounds, as a result of which the superiority of these compounds has been made apparent. Briefly, this test involves measuring the number of instances per unit time of motor operation in which flames occur in the combustion chamber prior to the time at which the normal flame produced by the spark occurs, in general following the procedure described by Hirschler, McCullough and Hall, SAE Trans, 62, 40 (1954). Efliciency of the preignition additive can be measured by the preignition index, which is a percentage of such abnormal flames occuring in the additive-containing test gasoline as compared with the base fuel, i.e., the same TEL-containing gasoline which has not been treated with the preignition additive.

Obviously, many modifications and variations of this invention may be made Without departing from the spirit and scope thereof and only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. Compounds of the general formula R R"P:BRYX wherein R is a lower alkyl radical, R" is selected from the group consisting of lower alkyl and phenyl radicals, R is selected from the class consisting of a lower alkyl radical, a phenyl radical and a lower alkyl-substituted phenyl radical, X is selected from the group consisting of O1 and Br and Y is selected from the group consisting of Cl, Br, lower alkyl, phenyl, and a lower alkyl-substituted phenyl.

. The compound (C H P:BCl C H The compound (C H P:BBr C H Th compound (C2H5)3PIBC12C2H5. The compound (C H P:BCl C I-I The compound (C2H5)3PIBC12C3H7.

Hewitt et al.: J. Chem. Soc. (London), volume of 1953, pages 530-534. 

1. COMPOUNDS OF THE GENERAL FORMULA R2R"P:BR''YX WHEREIN R IS A LOWER ALKYL RADICAL, R" IS SELECTED FROM THE GROUP CONSISTING OF LOWER ALKYL AND PHENOL RADICALS, R'' IS SELECTED FROM THE CLASS CONSISTING OF A LOWER ALKYL RADICAL, A PHENYL RADICAL AND A LOWER ALKYL-SUBSTITUTED PHENYL RADICAL, X IS SELECTED FROM THE GROUP CONSISTING OF CL AND BR AND Y IS SELECTED FROM THE GROUP CONSISTING OF CL, BR, LOWER ALKYL, PHENOYL, AND A LOWER ALKYL SUBSTITUTED PHENYL. 